设置了TTL的数据 根据TTL大小分桶
每个bucket的大小由最大的TTL和 evict-hist-buckets来决定
bucket_width = max_ttl / evict-hist-buckets

evict-hist-buckets可以基于namespace设置 可以动态修改

high-water-memory-pct  high-water-disk-pct 设置 evict 逐出时机
容量超出阈值  等待nsup线程启动 逐出数据
NSUP （namespace supervisor）  负责 过期 和 逐出操作

逐出以bucket为单位，不能只逐出部分
极端情况下 ，数据全部集中在第一个桶 ， 不可能全部逐出
bucket中的数量少于evict-tenths-pct 的数量 ，太会逐出

逐出机制 比 Redis 更精细
不过可能需要手工调整 或者 根本没法逐出

tenths 十分之一
evict-tenths-pct   百分比十分之一  相当于千分之几
ns->evict_tenths_pct = 5; // default eviction amount is 0.5%

base/namespace.c

ns->evict_hist_buckets = 10000; // for 30 day TTL, bucket width is 4 minutes 20 seconds
ns->evict_tenths_pct = 5; // default eviction amount is 0.5%

ns->hwm_disk_pct = 50; // evict when device usage exceeds 50%
ns->hwm_memory_pct = 60; // evict when memory usage exceeds 50% of namespace memory-size
ns->max_ttl = MAX_ALLOWED_TTL; // 10 years
ns->stop_writes_pct = 90; // stop writes when 90% of either memory or disk is used
ns->storage_min_avail_pct = 5; // stop writes when < 5% disk is writable


TTL 分部查看
admin
show distribution 
ns1  TTL distribution in seconds
percentage of records having ttl less than or equal to value measured in seconds


 asadm -e "show distribution"
~~~~~~~~~~~~~~~~~~~test - TTL Distribution in Seconds~~~~~~~~~~~~~~~~~~
      Percentage of records having ttl less than or equal to value
                          measured in Seconds
      Node   10%   20%   30%   40%   50%   60%   70%   80%   90%   100%
aerospike1     0     0     0     0     0     0     0     0     0      0
aerospike2     0     0     0     0     0     0     0     0     0      0
Number of rows: 2




 aerospike3.8及以上版本的数据淘汰机制 
 aerospike中的过期驱逐和停止写入机制